1. Field of the Invention
The present invention relates to a fuel cell which generates electricity through an electrochemical reaction of hydrogen and oxygen.
2. Description of the Related Art
Recently, fuel cells having high energy conversion efficiency and generating no toxic substances through an electricity generation reaction have attracted attention. As one of the fuel cells, there has been known a solid polymer type fuel cell which is allowed to operate at a low temperature of 100° C. or less.
The solid polymer type fuel cell is a device having a basic structure where a solid polymer membrane as an electrolyte membrane is disposed between a fuel electrode and an air electrode and allowing a fuel gas including hydrogen to be supplied to the fuel electrode and allowing an oxidant gas including oxygen to be supplied to the air electrode to generate electricity through the following electrochemical reaction.Fuel Electrode: H2→2H++2e−  (1)Air Electrode: ½O2+2H++2e−→H2O  (2)
Each of the anode and the cathode is configured with a structure where a catalyst layer and a gas diffusion layer (GDL) are stacked. The fuel cell is configured so that the catalyst layers of the electrodes are disposed to face each other with the solid polymer membrane interposed therebetween. The catalyst layer is a layer where carbon particles carrying catalyst are bound by an ion exchange resin. The gas diffusion layer becomes a passage of the oxidant gas or the fuel gas.
In the anode, the hydrogen included in the supplied fuel is decomposed into hydrogen ions and electrons as expressed by the above Formula (1). Among them, the hydrogen ions move through an inner portion of the solid polymer electrolyte membrane toward the air electrode, and electrons move through an external circuit toward the air electrode. On the other hand, in the cathode, the oxygen included in the oxidant gas supplied to the cathode react with the hydrogen ions and electrons moved from the fuel electrode to generate water as expressed by the above Formula (2). In this manner, since electrons move from the fuel electrode toward the air electrode in the external circuit, power is extracted.
For example, Patent Document 1 discloses a gas diffusion electrode for a fuel cell where an amount of a water repellant in a porous substrate is continuously changed from a side which is in contact with a catalyst layer toward the other side. In addition, Patent Document 2 discloses a technique for suppressing excessive immersion of a fluid material at a first exposed surface of a substrate in a thickness direction of the substrate by allowing a half or more of a second exposed surface of the substrate not to be in contact with a supporting member or by allowing a supporting surface of the supporting member to have a water repelling property in a gas diffusion layer.